05.09.2024 – Hitchhikers. Part 1.

Three different species were found on our trips today: Rough-toothed (Steno bredanensis), Atlantic spotted (Stenella frontalis) and Bottlenose (Tursiops truncatus) dolphins. I have to admit, the morning trip went through quite large swells, making some of our guests reconsider a second career as sailors. Luckly, in the afternoon, we found a group of Bottlenose dolphins in calm waters much closer to shore. Probably the best known dolphin species, it is the kind of animal that everyone imagines when we speak about “dolphins”. Other than you might expect, instead of leaping acrobatically out of the blue, they mostly swim particularly calm alongside the boats. Calm enough to observe details: Eventually a glimpse into their eyes, the different shapes of their dorsal fins, the different colours of their skin, the abundant scars on their bodies, the shiny blue cucumber-shaped eruption on their skin…? Dear readers, don’t worry, our dolphins were fine. They were just carrying a hitchhiker on their back for a while.

There are all kinds of animals in the ocean that attach to other marine wildlife in order to get a ride. Most of them are not considered parasites, as the worst damage they are producing is elevated weight and drag. The weird looking creature on our Bottlenose dolphin was a Remora fish (Echeneidae). They are also known as suckerfish, diskfish or whalesucker (Remora australis). Latter has, as the name suggests, specialized to attach to cetaceans. But Remoras in general take a ride on any large marine animal they can find. Besides whales or dolphins, also turtles, sharks, manta rays or manatees and even ships will find themselves regularly in these rather one-sided friendships. While well protected from predators during the free ride, the lazy fish just open their mouth and filter-feed on zooplankton and eventually also whale’s leftovers. We are speaking of all kinds of leftovers – whatever the whale or dolphin just hunted, but also the whale’s old skin and faeces. Eventually, they will even use the platform of their hosts as a meeting point between males and females. Enough weird facts? Remoras have remarkable adaptations indeed. In order to attach, they use a flat, oval suction disk (shoe-sole looking if you ask me). This suction disk has tooth-like slats and can produce a vacuum in order to attach. Surprisingly, this structure has been modified from the Remora fish’s first dorsal fin. In other words, Remoras will have to swim upside down when attached to their hosts. Not such a comfortable ride it seems, after all? Especially not once the dolphins have enough of their hitchhikers – on some occasions, they make the craziest leaps out of the sea to get rid of Remora fish. After a number of slaps onto the ocean surface, the dolphin often manages to shake the fish off, probably leaving a confused hitchhiker behind. Remoras are not the only creatures that like to attach to whales and dolphins. But this was enough information to fill a night of sweet dreams, am I right?

By Sarah Kather

Sightings of the day

Ribeira Brava

09:30 Atlantic spotted dolphins, Rough-toothed dolphins

13:30 Bottlenose dolphins

Stenella

09:30  Atlantic spotted dolphins, Rough-toothed dolphins

14:00  Bottlenose dolphins, Atlantic spotted dolphins

17:00 Bottlenose dolphins, Atlantic spotted dolphins